This application claims the priority of German Application No. 197 26 723.8, filed Jun. 24, 1997.
The invention relates to a process for manufacturing a vehicle body shell for a passenger car which has a forward structure provided with two side members and a forward cross member, an assembly cross member being joined to the side members, on which assembly cross member lower control arms of an axle are disposed, upper control arms being connected by way of two consoles with wheel installation units which are linked to the assigned side members.
In the case of Mercedes-Benz passenger cars, it is known to provide the forward structure of a body shell of a passenger car with an assembly cross member called an integral support which is linked from below to two side members of the forward structure. The assembly cross member, in particular, carries the engine, the steering system and the lower control arms of an axle whose upper control arms are disposed in the area of the wheel installation plates of the forward structure which are connected with the side members. Since the assembly cross member, as a separate component, after the completion of the forward structure, is joined from below to the side members during the overall assembling of the vehicle, tolerances occur on the suspension elements and damping elements as well as, in particular, between the upper and the lower bearing points for the control arms of the axle. This subsequently requires a high-expenditure adjustment of the wheel position angle on the axle.
It is an object of the invention to provide a manufacturing process of the above-mentioned type which considerably reduces the expenditures for finishing operations.
This object is achieved in that the bearing points of each wheel installation unit, which are situated behind one another in the longitudinal direction of the vehicle, for the upper control arm bearing, by means of a tensioning of the wheel installation unit, are brought to a defined distance range with respect to a central fixing in the transverse direction of the vehicle. A position of the side members which is identical with respect to the longitudinal direction of the vehicle with the fixing holes in the forward structure, which are punched in the component part, is established by a fastening on the fastening surfaces.
By means of the above-solution according to the present invention, it is possible to link the assembly cross member largely without tolerances, whereby later finishing operations for the adjustment of the various axle geometries are avoided. The solution according to the invention therefore provides a precisely symmetrical arrangement of the front axle by the appropriate selection of defined reference points. During the attaching of the wheel installation units with the side members to the shell body, these are fastened at a central fixation of the forward structure relative to the longitudinal and transverse direction of the vehicle at a fixed distance in parallel thereto in the transverse direction of the vehicle and at a positioning notch in the longitudinal direction of the vehicle. By means of the solution according to the invention, it is therefore possible to eliminate a first or basic adjustment of the axle geometry in a reliable manner with respect to the manufacturing process, whereby finishing operations are avoided.
According to the invention, the wheel installation units are therefore aligned on the left and on the right on the side member in parallel to the longitudinal direction of the vehicle relative to the positioning frame. In the transverse direction of the vehicle, the side members are fixed in parallel at a very precise distance with the aid of the connection points placed in the pressed part by means of fixing aids. The forward structure is then welded together. For placing the fastening bores for the upper transverse control arms for the position in the transverse direction of the vehicle relative to the lower axle pivot points, with respect to the described fixing system in the side member, the vehicle transverse direction position is measured and, relative thereto, the fastening holes for the upper transverse control arms are placed at a fixed distance.
As a further development of the invention, the forward structure is aligned and welded with respect to the body shell on a positioning frame axially symmetrical to a longitudinal center line. This provides the prerequisites for achieving a symmetrical arrangement of the assembly cross member and of the various bearing points of the front axle.
In a further development of the invention, the assembly cross member is aligned and positioned with the lower linking points of the axle relative to the consoles on the wheel installation unit for the fastening of the upper transverse control arms of an axle. In this case, fixing points on the side members are utilized in the longitudinal direction of the vehicle and one of these fixing points is utilized in the transverse direction of the vehicle for the positioning of the assembly cross member in the vehicle relative to the consoles of the upper control arm of an axle. On the assembly cross member, fixing aids are also installed relative to the lower linking points of the axle which fit into the fixing points on the side member structure of the body. This considerably reduces tolerances with respect to the linking of the assembly cross member to the body.